Method for controlling integrated renewable electric generation resource and charge storage system providing desired capacity factor

ABSTRACT

Methods for controlling an integrated renewable energy source (RES) and energy storage system (ESS) of a RES-ESS facility having a point of grid interconnect (POGI) limit are provided. A forecast for energy production of the RES as well as a state of charge (SOC) schedule are used to calculate a SOC target-based POGI cap that is less than the POGI limit, with the SOC target-based POGI cap representing as low a peak power output value as possible while still ensuring satisfaction of the SOC schedule. The forecasted RES production, SOC schedule, and SOC target-based POGI cap are used to generate a time-varying charge/discharge control signal for the ESS that ensures the SOC schedule is satisfied.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.17/120,019, filed Dec. 11, 2020, now U.S. Pat. No. 11,043,809, to issueJun. 22, 2021, which claims priority to U.S. Provisional PatentApplication No. 63/020,009 filed on May 4, 2020, wherein the entiredisclosure of the foregoing application is hereby incorporated byreference herein.

TECHNICAL FIELD

Subject matter herein relates to an integrated renewable electricalenergy generation resource and energy storage facility configured tosupply an aggregated power output to an electrical grid, as well asmethods for controlling such a facility and implementing power deliverytransactions for potential energy outputs of such a facility.

BACKGROUND

A substantial increase of renewable electric generation resources, suchas solar photovoltaic (PV) and wind power generators, has taken place inrecent years. The unsteady nature of solar and wind generation due tonatural and meteorological conditions can result in network frequencyand voltage deviations. As renewable electric generation resources startto provide a greater percentage of electrical supply and displacetraditional base-load electrical generation units such as coal-fired andnuclear-powered units, technical challenges are introduced, such as gridinterconnection, power quality, reliability, stability, protection, andgeneration dispatch and control. The intermittent nature of solar andwind generation and rapid fluctuation in their output make theircombination with energy storage devices (such as a battery energystorage system or BESS) attractive to enhance compatibility withelectrical grids, such as to smooth fluctuations and enhancepredictability of energy supplied to a grid from a renewable generationresource. Conventional renewable energy resources have relatively lowcapacity factors roughly tied to the capacity factor of the resource(e.g., for solar typically 20% to 40% depending on location and weatherpattern). When renewable energy resources replace traditionalfossil-fired baseload power plants, they under-utilize existingtransmission infrastructure. This may require building new transmissioninfrastructure, which is costly, time-consuming, and challenging (e.g.,including the need to obtain permitting), thereby increasing costs permegawatt-hour produced, delays, and risk in incorporating renewablegeneration into existing grids.

Co-locating renewable electric generation and electrical energy storagedevices may provide cost savings by reducing costs related to sitepreparation, land acquisition, permitting, interconnection, installationlabor, hardware, and overhead. Additionally, tax savings may result,typically if the electrical energy storage devices are subject to beingcharged exclusively from on-site renewable electric generationresources, and co-location of generation and storage device alsominimizes transmission losses therebetween.

Energy storage devices may be used to support arbitrage, which involvescharging a storage device during hours when energy prices are low, anddischarging a storage device during hours during more expensive peakdemand hours. Energy storage devices may also be used to promoteload-leveling, to more efficiently coordinate the dispatch of multiplegeneration resources.

To illustrate the principles of smoothing production variations andarbitrage, reference is made to FIG. 1, which is an output plot for aconventional RES-ESS facility (including a photovoltaic (PV) array and aBESS), showing superimposed plots of PV production, combined PV plusBESS output, and BESS state of charge (SOC) for hours of 06:00 to 22:00for one day. As shown, PV output starts around 07:00, increases to amaximum value near 12:00, and decreases to zero around 17:00, withsignificant fluctuation in PV output. Since some of the PV output isused to charge the BESS (i.e., increase the SOC), amplitude variationsof the combined PV plus BESS output are significantly attenuated incomparison to the PV output. Additionally, energy stored in the BESS isdischarged between 17:00 and 21:00, enabling shifting of sales frommid-day power production to evening hours when energy prices are higherthan during the day. Despite the benefits of production variationsmoothing and arbitrage provided by the PV array and BESS utilized inFIG. 1, the combined PV plus BESS output still exhibit very significantvariation during a calendar day, such that the PV plus BESS system isnot suitable for providing a high level of fixed firm capacity for along duration.

Various considerations may affect utilization of a BESS. Lithium-basedbatteries can degrade at an accelerated rate when at or near a fullcharge capacity. Grid operators seeking to dispatch an integratedrenewable electric generation and charge storage facility may requireattainment of specific battery state of charge (SOC) conditions atparticular times in a given day (with SOC being generally defined as thepercentage of the full capacity of a battery that is still available forfurther discharge). Once a battery is at 100% SOC, it is also unable toabsorb rapid increases in electric power output of an associatedrenewable electric generation resource, such that any excess powergeneration not able to be accepted by an electrical grid may undesirablyneed to be curtailed (e.g., by clipping in a power inverter).

Further considerations that may affect utilization of a BESS include theability to provide (and the ability to be compensated for providing)ancillary services. Ancillary services help grid operators maintain areliable electricity system by ensuring that frequency, voltage, andpower load remain within certain limits. Classes of ancillary servicesinclude frequency maintenance (e.g., to address requirements forspinning reserve, energy balancing, and sheddable loads), voltagecompensation (e.g., to address power factor correction and energylosses/dissipation due to energy transport), operational management(e.g., to address grid monitoring, feed-in management, and redispatch),and reconstruction of supply (e.g., to facilitate rapid restarting of apower grid in case of a blackout). The variability and uncertainty ofrenewable energy resources (e.g., wind and solar generation) increasesthe requirements for various ancillary services, thereby affecting thescheduling and pricing of those services. If renewable energy producersare rewarded for energy generation alone, however, these producers maybe discouraged from providing ancillary services.

The transmission and distribution infrastructure of an electricity gridmust be sized to meet peak demand, which may only occur over a few hoursof a year. When anticipated growth in peak electricity demand exceedsthe existing capacity of the electricity grid, costly investments areneeded to upgrade equipment and develop new infrastructure.

An electrical energy generation resource may be coupled withtransmission resources of an electrical grid at a point of gridinterconnection (POGI), typically at a voltage of at least 33 kV or atleast 66 kV suitable for transmission of electric power over longdistances with acceptably low transmission losses. To ensure reliabilityand avoid damage to transmission resources, a POGI limit (representing amaximum power that may be supplied to a transmission resource) isestablished for each electrical energy generation resource. To increasethe revenue potential from a photovoltaic energy generation resource forassociated transmission resources of a predetermined cost, it iscommonplace for the aggregate output of a photovoltaic array to beoversized relative to a POGI limit, since peak photovoltaic generationmay only be infrequently achieved (e.g., due to factors such asunfavorable weather conditions, solar conditions, panel cleanlinessconditions, PV panel aging, and high ambient air temperatures thatreduce PV panel output). This oversizing of a photovoltaic array enablesan increased amount of power to be sold over the course of a year, butalso increases the need to curtail excess power (e.g., by inverterclipping) during peak irradiance periods. In order to avoid damage totransmission resources, however, interconnection procedures promulgatedby the Federal Energy Regulatory Commission (FERC) and rules provided inthe corresponding Large Generator Interconnection Agreement (LGIA)permit power supplied to a transmission system to exceed a point of gridinterconnect by a small technical tolerance of typically no greater than2%. These rules protect an electric grid from failure (e.g., due tooverloading of circuits, transmission lines, and transformers, ortriggering circuit breakers to disconnect an over-generating facility.Compliance with such rules is typically assured by providing invertersbetween a photovoltaic array and a transmission system that have a totaloutput capacity equal to the POGI limit, plus a small allowance forelectrical losses between the inverters and the grid interconnectionpoint.

In power purchase agreements for facilities that include utility scalerenewable generation sources paired with energy storage systems, theutility energy buyer commonly requires that the utility retain therights to determine the charge and discharge signals for the energystorage system. Thus, the utility's operating decisions would affecttotal generation output and revenue producing capability of the RES-ESSfacility, in ways that may not have been expected during the originalplanning for the project. Yet in the power purchase agreements for suchfacilities, the capital expenses for developing the projects aretypically amortized over the expected generation, and investors of theseprojects prefer certainty in the expected generation in order tocontribute capital for project funding.

Conventional renewable generation resources have had capacity factorsand load matching capability (e.g., timing) tied to availability of thedriving resource (e.g., solar irradiance or wind). Due to their lowcapacity factors and limited time availability, conventional renewablegeneration resources underutilize transmission resources. This is asignificant problem for utilities due to the cost and difficulty ofexpanding transmission resources.

In view of the foregoing, need exists for improved renewable electricalenergy generation resource and energy storage facilities, as well asmethods for controlling such facilities and for implementing powerdelivery transactions for outputs of such as facility.

SUMMARY

The present disclosure relates in various aspects to an integratedrenewable electrical energy generation resource and energy storagesystem (RES-ESS) facility configured to supply an aggregated poweroutput to an alternating current (AC) electrical grid, as well asmethods for controlling such a facility and implementing power deliverytransactions for potential energy outputs of such a facility. TheRES-ESS facility may be referred to as an “AC overbuilt” facility, withESS capacity and RES inverter capacity being larger than conventionalfacilities, and with RES inverter capacity being larger than a point ofgrid interconnect (POGI) limit for the facility. Systems and methodsdisclosed herein enable high capacity factors and production profilesthat match a desired load. A degree of oversizing may be selected at thetime of design and construction to permit an AC-overbuilt RES-ESSfacility to provide a fixed firm capacity for a desired capacity andduration, thereby permitting a RES-ESS facility to emulate (and serveas) a baseload power station. This capability represents a fundamentalshift relative to the conventional utilization of renewable energyresources involving significant output fluctuation and limited loadmatching capabilities, by permitting a RES-ESS facility to serve as agrid-tied renewable electric baseload generator.

In an AC overbuilt RES-ESS facility as described herein, the RES isconfigured to produce direct current (DC) electric power, and the ESS isconfigured to be charged with, and to discharge, DC electric power. Atleast one first power inverter associated with the RES is configured toconvert RES DC electric power to RES AC electric power, and at least onesecond power inverter associated with the ESS is configured to provideAC-DC conversion utility when charging the ESS with RES AC electricpower and to provide DC-AC conversion utility when discharging the ESSAC electric power to the electric grid. An aggregate output capacity ofthe at least one first power inverter is sized to exceed the POGI limitfor the facility, with the facility being configured to cause RES ACelectric power to be diverted (or otherwise provided) to the least onesecond power inverter to avoid supplying RES AC electric power to theelectric grid in excess of the POGI limit. A method for controlling aRES-ESS facility comprises using a time-dependent forecast of electricalenergy production by the RES and a state of charge (SOC) schedule forthe ESS to calculate a SOC target-based POGI cap that is less than the(predetermined fixed) POGI limit, with the SOC target-based POGI caprepresenting a peak power output value for the RES-ESS facility that isas low as possible while still ensuring that the SOC schedule issatisfied. The method further comprises using the SOC target-based POGIcap in conjunction with the time-dependent forecast of electrical energyproduction by the RES and the state of charge (SOC) schedule for the ESSto generate a time-varying charge/discharge control signal for the ESS,with the control signal being configured to ensure satisfaction of theSOC schedule. A method for implementing a power delivery transactionbetween a buyer and seller for potential electrical energy output of aRES-ESS facility includes periodically estimating total potentialelectrical energy output of the RES during at least one retrospectivetime windows utilizing a signal indicative of one or more sensedparameters, comparing the total potential electrical energy output ofthe RES to a POGI limit for the facility to identify potential RESovergeneration during the time window(s), identifying an amount ofcharged potential RES overgeneration that was charged to the ESS duringthe time window(s), and charging the buyer for undelivered electricalenergy if charged potential RES overgeneration is less than potentialRES overgeneration during the time window(s).

In one aspect, the disclosure relates to an integrated renewable energysource and energy storage system (RES-ESS) facility configured to supplyelectric power to an electric grid at a grid interconnection point andhaving a point of grid interconnect (POGI) limit representing a maximumelectric power value to be supplied from the RES-ESS facility to theelectric grid. In particular, the RES-ESS facility comprises: arenewable energy source (RES) configured to produce electric power,wherein the electric power produced by the RES comprises RES directcurrent (DC) electric power; at least one first power inverter coupledbetween the RES and the grid interconnection point, wherein the at leastone first power inverter is configured to convert RES DC electric powerto RES alternating current (AC) electric power; an energy storage system(ESS) configured to be charged with electric power produced by the RES;and at least one second power inverter coupled (i) between the ESS andthe grid interconnection point, and (ii) between the at least one firstpower inverter and the grid interconnection point, wherein the at leastone second power inverter is configured to (a) convert RES AC electricpower to ESS DC electric power when charging the ESS with RES ACelectric power, and (b) convert ESS DC electric power to ESS AC electricpower when discharging the ESS AC electric power to the electric grid;wherein an aggregate output capacity of the at least one first powerinverter is sized to exceed the POGI limit; and wherein the RES-ESSfacility is configured to divert RES AC electric power to the at leastone second power inverter in an amount sufficient to avoid supplying RESAC electric power to the electric grid in excess of the POGI limit

In certain embodiments, the aggregate output capacity of the at leastone first power inverter is sized to exceed the POGI limit by at least10%, by at least 30%, by at least 50%, by at least 70%, by at least100%, or another threshold specified herein, wherein the foregoingminimum thresholds may optionally be capped by the sum of (i) the POGIlimit and (ii) a capacity of the ESS. In certain embodiments, theaggregate output capacity of the at least one first power inverter issized to equal a sum of (i) the POGI limit and (ii) a capacity of theESS.

In certain embodiments, the RES comprises a photovoltaic array. Incertain embodiments, the RES comprises one or more wind turbines.

In certain embodiments, the RES-ESS facility is configured to supply ACelectric power to the electric grid at a voltage of at least 33 kV or atleast 66 kV.

In another aspect, the disclosure relates to a method for controlling anintegrated renewable energy source and energy storage system (RES-ESS)facility configured to supply electric power to an electric grid at agrid interconnection point, the RES-ESS facility including a renewableenergy source (RES) and an energy storage system (ESS) chargeable withelectric power produced by the RES, and the RES-ESS facility having apoint of grid interconnect (POGI) limit. The method comprises: providingat least one first power inverter coupled between the RES and the gridinterconnection point, wherein the at least one first power inverter isconfigured to convert RES DC electric power to RES alternating current(AC) electric power, and an aggregate output capacity of the at leastone first power inverter is sized to exceed the POGI limit; providing atleast one second power inverter coupled (i) between the ESS and the gridinterconnection point, and (ii) between the at least one first powerinverter and the grid interconnection point, wherein the at least onesecond power inverter is configured to (a) convert RES AC electric powerto ESS DC electric power when charging the ESS with RES AC electricpower, and (b) convert ESS DC electric power to ESS AC electric powerwhen discharging the ESS AC electric power to the electric grid; andwhile supplying a first portion of the RES AC electric power to theelectric grid, diverting a second portion of the RES AC electric powerto the at least one second power inverter in an amount sufficient toavoid supplying RES AC electric power to the electric grid in excess ofthe POGI limit.

In certain embodiments, the method further comprises supplying RES ACelectric power to the electric grid at a fixed firm capacity of at least80% (or at least 90%, or at least 95%, or 100%) of the POGI limit for aduration of at least 6 hours per day, at least 8 hours per day, or atleast 12 hours per day, or at least 16 hours per day, or anotherthreshold specified therein. In certain embodiments, the supplying ofRES AC electric power to the electric grid for the specified fixed firmcapacity and duration is performed for at least 90%, at least 95%, or atleast 99% of the days in a specified month or year. In certainembodiments, the RES comprises a photovoltaic array. In certainembodiments, RES AC electric power is supplied to the electric grid at avoltage of at least 33 kV or at least 66 kV (or at least 69 kV).

In another aspect, the disclosure relates to a method for controlling anintegrated renewable energy source and energy storage system (RES-ESS)facility configured to supply electric power to an electric grid, theRES-ESS facility including a renewable energy source (RES) and an energystorage system (ESS) chargeable with electric power produced by the RES,and the RES-ESS facility having a point of grid interconnect (POGI)limit. The method comprises: utilizing (A) a time-dependent forecast ofelectrical energy production by the RES and (B) a state of charge (SOC)schedule to calculate a SOC target-based POGI cap that is less than thePOGI limit, wherein the SOC target-based POGI cap represents a peakpower output value for the RES-ESS that is as low as possible whilestill ensuring that the SOC schedule is satisfied; and utilizing (A) thetime-dependent forecast of electrical energy production by the renewableelectrical energy generation resource, (B) the state of charge (SOC)schedule for the electrical energy storage device including at least oneSOC target value, and (C) the SOC target-based POGI cap, to generate atime-varying charge/discharge control signal for the ESS, wherein thetime-varying charge/discharge control signal is configured to ensurethat the SOC schedule is satisfied.

In certain embodiments, the method further comprises periodicallyupdating the generation of the time-varying charge/discharge controlsignal based upon at least one of the following items (i) or (ii): (i)an updated time-dependent forecast of electrical energy production; or(ii) an updated SOC schedule.

In certain embodiments, the method further comprises periodicallyupdating the generation of the time-varying control signal uponexpiration of a refresh period, wherein the periodic updating comprisescomputing and using a new basepoint value for aggregated energy suppliedfrom the RES and the ESS to an electrical grid upon expiration of therefresh period.

In certain embodiments, the refresh period is configurable by anoperator of the RES-ESS facility.

In certain embodiments, the ESS is charged exclusively from the RES.

In certain embodiments, the method further comprises altering thetime-varying charge/discharge control signal responsive to a differencebetween forecasted production and actual production of at least oneelectric generation facility to ensure that the SOC schedule issatisfied.

In certain embodiments, the RES comprises a photovoltaic array, the ESScomprises a battery array, and the time-dependent forecast of electricalenergy production comprises a solar production forecast.

In certain embodiments, the time-dependent forecast of electrical energyproduction comprises an ensemble based on of two or more of thefollowing: on-site sky imaging, satellite imaging, and meteorologicalmodeling.

In certain embodiments, the RES comprises at least one wind turbine, theESS comprises a battery array, and the time-dependent forecast ofelectrical energy production comprises a wind production forecast.

In certain embodiments, the method further comprises generating the SOCtarget-based POGI cap using a computer-implemented, iterativeroot-finding algorithm.

In certain embodiments, the method further comprises generating the SOCtarget-based POGI cap using a computer-implemented, matrix-basedroot-finding algorithm.

In another aspect, the disclosure relates to a method for implementing apower delivery transaction between a buyer and seller for potentialelectrical energy output of an integrated renewable energy source andenergy storage system (RES-ESS) facility that includes a renewableenergy source (RES) and an energy storage system (ESS). The methodcomprises: periodically estimating total potential electrical energyoutput of the RES during at least one retrospective time windowutilizing a signal indicative of one or more sensed parameters;comparing the estimated total potential electrical energy output of theRES to a point of grid interconnect (POGI) limit for the RES-ESSfacility to identify potential RES overgeneration during the at leastone retrospective time window, wherein potential RES overgenerationequals potential RES electrical energy output in excess of the POGIlimit during the at least one retrospective time window; identifying anamount of charged potential RES overgeneration, calculated as potentialRES overgeneration charged to the ESS during the at least oneretrospective time window; and charging the buyer for undeliveredelectrical energy if charged potential RES overgeneration is less thanpotential RES overgeneration during one or more time windows of the atleast one retrospective time window.

In certain embodiments, the method further comprises identifying anamount of uncharged potential RES overgeneration, calculated aspotential RES overgeneration not charged to the ESS during the at leastone retrospective time window; wherein an amount charged to the forundelivered electrical energy is based on a deemed delivered RESovergeneration value that is identified according to the followinglogical sequence: (i) if potential RES overgeneration equals zero, thenthe deemed delivered RES overgeneration value equals zero, else (ii) ifcharged potential RES overgeneration is greater than or equal topotential RES overgeneration, then the deemed delivered RESovergeneration value equals zero, else (iii) if charged RESovergeneration is less than potential RES overgeneration, then thedeemed delivered RES overgeneration value equals the lesser of thefollowing items (a) and (b): (a) uncharged potential RES overgeneration,and (b) potential RES overgeneration minus charged RES overgeneration.

In certain embodiments, the at least one retrospective time windowcomprises a plurality of time periods. In certain embodiments each timeperiod of the plurality of time periods is less than one hour (e.g.,each time period may be five minutes, one minute, or another suitableinterval).

In certain embodiments, the one or more time windows comprises asummation of multiple time windows of the at least one retrospectivetime window. In certain embodiments, the summation of multiple timewindows corresponds to a period of one day.

In certain embodiments, the method further comprises capping the amountof charged potential RES overgeneration based on a capacity of the ESS,if the potential RES overgeneration exceeds a capacity of the ESS.

In certain embodiments, the RES comprises a photovoltaic array, and theone or more sensed parameters comprise irradiance sensed at one or morelocations at the RES-ESS facility.

In certain embodiments, the RES comprises one or more wind turbines, andthe one or more sensed parameters comprise wind speed sensed at one ormore locations at or above the RES-ESS facility.

In certain embodiments, the RES-ESS facility is configured to supplyenergy to an electrical grid at a voltage of at least 33 kV or at least66 kV. In certain embodiments, the ESS is configured to be changedexclusively from the RES.

In another aspect, any of the foregoing aspects, and/or various separateaspects and features as described herein, may be combined for additionaladvantage. Any of the various features and elements as disclosed hereinmay be combined with one or more other disclosed features and elementsunless indicated to the contrary herein.

Other aspects, features and embodiments of the present disclosure willbe more fully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings incorporated in and forming a part of thisspecification illustrate several aspects of the disclosure, and togetherwith the description serve to explain the principles of the disclosure.

FIG. 1 is an output plot for a conventional RES-ESS facility (includinga photovoltaic array and battery storage), showing superimposed plots ofRES production, combined RES-ESS output, and ESS state of charge.

FIG. 2 is a schematic diagram of an AC-coupled RES-ESS facility coupledto an AC electric grid, showing a first power inverter associated with aRES and a second power inverter associated with an ESS.

FIG. 3 is a schematic diagram of a DC-coupled RES-ESS facility coupledto an AC electric grid, showing a DC/DC converter associated with an ESSand a power inverter that provides power conversion utility for both theRES and ESS.

FIG. 4A is a schematic diagram showing interconnections between variouscomponents of an AC coupled metering and control system for controllinga renewable energy source and energy storage system (e.g., aphotovoltaic (PV) array and a battery array chargeable with electricpower produced by the PV array) according to one embodiment of thepresent disclosure.

FIG. 4B is a schematic diagram showing certain components of the ACcoupled metering and control system of FIG. 4A.

FIG. 5 is a block diagram for a processor-based energy dispatch controlsystem for dispatching a renewable electrical energy generation resourceand an electrical energy storage device chargeable with electric powerproduced by the renewable electrical energy generation resourceaccording to one embodiment of the present disclosure.

FIG. 6A is a diagram showing relative sizes of a RES, a power inverter,and a point of grid interconnect limit for a conventional RES facilitycoupled with an AC electric grid.

FIG. 6B is a diagram showing relative sizes of a RES, a power inverter,and a point of grid interconnect limit for an AC overbuilt RES-ESSfacility according to one embodiment of the present disclosure.

FIG. 6C is a diagram showing relative sizes of a RES, a power inverter,and a point of grid interconnect limit for a DC-coupled RES-ESSfacility, to permit comparison to FIG. 6B.

FIG. 7A is a modeled output plot for an AC-coupled RES-ESS facilityhaving power inverter capacity matched to a point of grid interconnectlimit, with superimposed plots of RES production and combined RES-ESSoutput.

FIG. 7B is a modeled output plot for an AC overbuilt RES-ESS facilityhaving power inverter capacity that exceeds a point of grid interconnectlimit according to one embodiment of the present disclosure, withsuperimposed plots of RES production and combined RES-ESS output.

FIG. 8 is a modeled output plot for an AC overbuilt RES-ESS facilityhaving power inverter capacity that exceeds a point of grid interconnectlimit according to one embodiment of the present disclosure, withsuperimposed plots of RES production, combined RES-ESS output, and stateof charge of the ESS.

FIG. 9A is a modeled output plot for an AC-coupled RES-ESS facilityhaving power inverter capacity matched to a point of grid interconnectlimit, with superimposed plots of RES production, combined RES-ESSoutput, state of charge of the ESS, and ESS power output.

FIG. 9B is a modeled output plot for an AC overbuilt RES-ESS facilityhaving power inverter capacity that exceeds a point of grid interconnectlimit according to one embodiment of the present disclosure, withsuperimposed plots of RES production, combined RES-ESS output, state ofcharge of the ESS, and ESS power output.

FIG. 10 is a modeled output plot for an AC overbuilt RES-ESS facilityhaving power inverter capacity that exceeds a point of grid interconnectlimit according to one embodiment of the present disclosure, showingresults of utilizing a SOC target-based POGI cap, with superimposedplots of RES production, combined RES-ESS output, state of charge of theESS, and ESS power output.

FIG. 11 is a schematic diagram of a generalized representation of acomputer system that can be included as one or more components of asystem for controlling a RES-ESS facility according to one embodiment ofthe present disclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the embodiments andillustrate the best mode of practicing the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein, but it should be understood that such concepts andapplications are intended to fall within the scope of the disclosure andthe accompanying claims.

It will be understood that, although the terms “first,” “second,” etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including” when used herein specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

Embodiments described in the present application document include orutility an integrated renewable energy source (“RES”) (e.g., PV, wind,etc.) and energy storage system (“ESS′) facility or plant, wherein thecombination may be referred to here as RES-ESS or a RES-ESS facility (ofwhich a photovoltaic plus storage or “PV+S” facility is a subset). ARES-ESS facility can reach a desired SOC by charging the ESS with powerproduced by the RES. In certain embodiments, a RES-ESS facility willreach the desired SOC by prioritizing charging at times when RESgeneration is high. For example, an ESS may be charged more when moreRES generation is available, and an ESS may be charged less (or not atall) when RES generation is limited. The ESS may be discharged when RESgeneration is limited or unavailable.

In certain embodiments, a RES-ESS facility will charge the ESSexclusively from the RES, so that a maximum investment tax credit (ITC)can be utilized to reduce the effective cost of the facility. In certainembodiments, the ESS may additionally be charged from an electric gridconnected to the RES-ESS facility.

To provide context for a subsequent discussion of coupling between aRES-ESS facility and an AC electric grid, reference is made to FIGS. 1and 2.

FIG. 2 is a schematic diagram of an AC-coupled RES-ESS facility 10coupled to an AC electric grid 15, showing a first power inverter 14(e.g., a DC/AC inverter) associated with a RES 12 (e.g., a photovoltaicarray) and a second power inverter 18 (e.g., a DC/AC inverter)associated with an ESS 16 (e.g., one or more batteries). The first powerinverter 14 is coupled between the RES 12 and a grid interconnectionpoint 19. The second power inverter 18 is coupled (i) between the ESS 26and the grid interconnection point 19, and (ii) between the first powerinverter 14 and the grid interconnection point 19. The RES 12 isconfigured to produce DC electric power, and the first power inverter 14converts the RES DC electric power to RES AC electric power. The secondpower inverter 18 is configured to (a) convert RES AC electric power toESS DC electric power when charging the ESS 16 with RES AC electricpower, and (b) convert ESS DC electric power to ESS AC electric powerwhen discharging the ESS AC electric power to the electric grid 15. Inthis regard, the second power inverter 18 provides bidirectional powerconversion utility. The ESS 16 (e.g., batteries) and second powerinverter 18 may be located in a single area (e.g., a single centralizedenclosure) to provide lower costs of installation and maintenance.Although the first and second power inverters 14, 18 have been describedin a singular sense, it is to be appreciated that the first powerinverter 14 and the second power inverter 18 each represents at leastone power inverter that may encompass any suitable number of individualpower inverters.

FIG. 3 is a schematic diagram of a DC-coupled RES-ESS facility 20coupled to an AC electric grid 25, showing a DC/DC converter 28associated with an ESS 26 and a power inverter 29 that provides powerconversion utility for both the RES 22 and the ESS 26. The powerinverter 29 functions to convert DC electric power received from the RES22 and/or the ESS 26 to AC electric power to feed AC electric powerthrough a grid interconnection point 29 to the AC electric grid 25.

Although a DC-coupled RES-ESS facility 20 according to FIG. 3 mayexhibit lower conversion losses (due to reduced need for powerconversion), components (e.g., batteries) of the ESS 26 may need to bespread around a RES-ESS facility 20 proximate to components of the RES22 to avoid low voltage power dissipation. This necessitates anincreased number of containers or enclosures for components of the ESS26, thereby increasing costs for installation and maintenance. Thecapital cost for a DC-coupled RES-ESS facility 20 according to FIG. 3 isexpected to be higher than an AC-coupled RES-ESS facility 10 accordingto FIG. 2.

One aspect of the present disclosure is directed to an “AC overbuilt”RES-ESS facility, with ESS capacity and RES inverter capacity beinglarger than conventional facilities, and with RES inverter capacitybeing larger than a point of grid interconnect (POGI) limit for thefacility. Before discussing an AC overbuilt RES-ESS system in greaterdetail, however, components of a RES-ESS facility and an accompanyingutility interface will be introduced first, with reference to FIGS. 4A,4B, and 5.

FIG. 4A is a schematic diagram showing interconnections between variouscomponents of an AC coupled metering and control system 30 forcontrolling a renewable electrical energy generation device 34 includingmultiple generation units 34A-34N (such as a photovoltaic (PV) arrayincluding photovoltaic units) and an energy storage device 44 includingmultiple energy storage units 44A-44N (such as a battery array includingbattery units) chargeable with electric power produced by the renewableelectrical energy generation device 34 in a RES-ESS facility 31according to one embodiment. The RES-ESS facility 31 may combine arenewable electrical energy generation device 34 (e.g., such as an arrayof PV panels, wind turbines, or the like), and an energy storage device44 (e.g., an array of lithium-based batteries) that may be coupled to asingle substation 50 and/or located in a single property, area, orstructure.

FIG. 4A illustrates an AC-coupled RES-ESS facility 31 that uses powerinverters 36, 46 (e.g., rectifier-based or other appropriate powerconverters) to convert DC power produced by a renewable electricalenergy generation device 34 (e.g., a PV array in certain embodiments) orpower released by the energy storage device 44 to AC power for couplingto an AC electrical grid 54), but in certain embodiments, the RES-ESSfacility 31 may embody a DC coupled RES-ESS facility.

In certain embodiments, an energy storage device 44 may include at leastone of (or a combination of) batteries 44A, 44B using variousconstructions and chemistries, capacitors, or mechanical energy storagedevices such as flywheels or pumped-hydro installations. In certainembodiments, an energy storage device 44 may include at least onehydrolysis unit (e.g., configured to electrolyze water to releasehydrogen), optionally combined with hydrogen consuming electricityproducing element (e.g., a fuel cell array or gas turbine) and/or ahydrogen storage unit (e.g., adsorbent media for releasably bindinghydrogen, storage vessels, and/or reversible chemical reactant vesselsor beds).

In certain embodiments, a fast-following load may be substituted for anESS to effectuate smoothing of output of a RES facility at a POGI limit.A fast-following load may dissipate energy quickly (e.g., for industrialuse) without necessarily promoting energy storage. One non-limitingexample of a fast-following load would be a rock crusher.

Control methods involving a RES-ESS facility as disclosed herein mayutilize accurate renewable energy production forecasts (e.g., for PVproduction or wind production) into implementations for controllingcomponents of a RES-ESS facility, as well as state of charge (SOC)schedules for an ESS of such a facility.

In certain embodiments, a RES-ESS dispatcher unit 56 has the ability tocontrol the charge or discharge of the energy storage device 44 (e.g.,batteries) by communicating with an ESS controller 42, which may belocated in the RES-ESS facility 31. A RESSCADA (supervisory control anddata acquisition) controller 32 is operatively coupled with RESinverters 36 associated with the renewable electrical energy generationdevice 34 (optionally embodied in a PV array), and the ESS controller 42is operatively coupled with ESS inverters 46 associated with the energystorage device 44, with both the RESSCADA controller 32 and the ESScontroller 42 being in communication with the RES-ESS dispatcher unit56. In certain embodiments, a utility control center 58 (e.g., of anelectric power utility or grid operator) may communicate with theRES-ESS dispatcher unit 56 using DNP3 and set different configurationoptions. Additionally, the RES-ESS dispatcher unit 56 receives (orgenerates) an accurate renewable generation forecast (e.g., solargeneration forecast) that it uses to implement any desired controlmodes. As shown in FIG. 3A, certain embodiments may utilize readilyavailable electric power meters, such as a RES+ESS electrical powermeter 52 to measure RES-ESS (e.g., PV+S) facility output, a RESelectrical power meter 39 to measure RES output, and an ESS electricalpower meter 49 to measure ESS output. Signals from the RES electricalpower meter 39 are provided to the RESSCADA controller 32, and signalsfrom the ESS electrical power meter 49 are provided to the ESScontroller 42. The electric power generated by the RES-ESS facility 31may be provided to an electric power system (e.g., an AC electrical grid54) via a generator step-up (GSU) substation 50 that implementsprotection and appropriate voltage conversion. RES transformers 38 andESS transformers 48 may be arranged between the inverters 36, 46,respectively, and the GSU substation 50 to provide voltage conversionutility (e.g., to supply AC power signals to the GSU substation 50 at34.5 kV in certain implementations).

FIG. 4B is a schematic diagram showing certain components of the ACcoupled metering and control system of FIG. 4A, includinginterconnection of control- and sensor-related components. As shown inFIG. 4B, the RES-ESS dispatcher unit 56 is arranged between a utilitycontrol center 58 and a RES-ESS facility 31. Within the RES-ESS facility31, a RESSCADA controller 32 is operatively coupled with RES inverters36A-36N (wherein N represents any suitable number) that are configuredto provide AC conversion of DC power produced by renewable electricalenergy generation units 34A-34N (e.g., arrangeable as parts of arenewable electrical energy generation device 34). Similarly, within theRES-ESS facility 31, an ESS controller 42 is operatively coupled withESS inverters 46A-46N that are configured to provide AC conversion of DCpower supplied by energy storage units 44A-44N (e.g., arrangeable asparts of an energy storage device 44). The RES-ESS facility 31 furtherincludes at least one sensor 50, which may comprise one or more skyimaging sensors useful to determine sky conditions (such as presence ofclouds) proximate to the RES-ESS facility 31, with output signals fromthe at least one sensor 50 being supplied to the RES-ESS dispatcher unit56. The RES-ESS dispatcher unit 56 may also receive: (i) signals fromone or more sensors 62 (e.g., satellite imaging sensors or the like) notnecessarily associated with the RES-ESS facility 31; (ii) meteorologicaldata provided by a meteorological modeling unit 64; (iii) signals from aforecasting unit 66 that may forecast generation by the renewableelectrical energy generation device 34 and/or one or more otherrenewable electrical energy generation devices or units. In certainembodiments, time-dependent forecasting of electrical energy productionmay be performed by the forecasting unit 66 or may be performed by theRES-ESS dispatcher unit 56. In certain embodiments, a time-dependentforecast of electrical energy production may utilize one, two, or allthree (e.g., as an ensemble of two or more) of the following: on-sitesky imaging provided by the sensor(s) 50, satellite imaging provided bythe sensor(s) 62, and meteorological data provided by the meteorologicalmodeling unit 64. In certain embodiments, sensors of other types may beused.

FIG. 5 is a block diagram showing for a processor-based energy dispatchcontrol system 70 for dispatching a RES-ESS facility (e.g., includingrenewable electrical energy generation resource and an electrical energystorage device chargeable with electric power produced by the renewableelectrical energy generation resource) according to one embodiment. Thecontrol system 80 includes as functional blocks a utility interface 72,manual inputs 74, a settings combiner 76, and an energy dispatcher 78.The utility interface 72 communicates with an electric power systemutility, and with the energy dispatcher 78 to receive configurationcommands (e.g., mode configuration commands) and send plant status andstate information 82. An example of a coordinated charge-discharge modeconfiguration set by a utility may be a schedule that contains a firstSOC target at a pre-determined time, and a second SOC target at a secondpre-determined time. For example, the utility may want the ESS to reachan SOC of 90% by 5:00 PM and an SOC of 10% by 10:00 PM. The utilityinterface 72 receives DNP3 (Distributed Network Protocol) informationvia a DNP3 link 70, and is responsible for converting the published DNP3configuration points to internal data structures. The utility interface72 is also responsible for communicating any data structure changes backto the utility via the DNP3 link 80. Manual inputs 74 includeconfiguration parameters that are not addressable by MESA-ESS SCADApoints. The settings combiner 76 validates any configuration inputs andpasses them to the energy dispatcher 78 in one implementation. Thesettings combiner 76 receives MESA-ESS schedules/modes/curves providedby a utility or grid operator, receives schedules produced by anoptimizer, and receives any potential manual inputs 74, and thenproduces combined schedules/modes/curves. The energy dispatcher 78 is anengine that executes control modes for the RES-ESS facility (or plant)and decides on the charge or discharge level of the ESS utilizing arenewable energy production forecast 84. The energy dispatcher 78 isresponsible for controlling output of a RES-ESS facility in short timescales by observing the current state of the RES-ESS facility, utilizingtime-dependent forecasts of electrical energy production by the RES, andutilizing any combined MESA-ESS schedules/modes/curves produced by thesettings combiner 76. A renewable energy forecast may contain a timeseries of points for the power expected to be generated by the renewableenergy source (e.g., PV array, wind turbine, etc.). Such a forecast mayhave a format of (timestamp, power value) and contain a set of timevalues of specified intervals (e.g., 15 minutes in 1 minute intervals,36 hours in 1 hour intervals, etc.). These potential formats andtimeframes are provided to illustrate the nature of an exemplaryforecast, and are not intended to limit the disclosure. The energydispatcher 78 is also responsible for passing alerts and RES-ESS plantstate and/or status information back to the utility interface 72.

Having described components of a RES-ESS facility, an AC overbuiltfacility will now be described.

A. AC Overbuilt RES-ESS Facility

One aspect of the present disclosure is directed to an “AC overbuilt”RES-ESS facility, embodying an AC-coupled RES-ESS facility with ESScapacity and RES inverter capacity being larger than conventionalfacilities, and with RES inverter capacity being larger than a point ofgrid interconnect (POGI) limit for the facility. This permits a RES tobe significantly oversized relative to a POGI limit without requiringgeneration in excess of the POGI limit to be curtailed, since the excessgeneration may be captured by the ESS. An AC overbuilt RES-ESS facilitymay be configured to supply power to an AC electric grid at the POGIlimit, while simultaneously supplying power to an ESS. In such afacility, a large-capacity ESS (or a fast-following load) is used as aload to absorb RES generation in excess of the POGI limit, to ensurethat power is supplied from the RES-ESS facility at a level notexceeding the POGI limit for the facility.

An AC overbuilt RES-ESS facility is suitable for providing a high levelof fixed firm capacity for a long duration, in contrast to aconventional RES-ESS facility that typically provides peaking utility. Aconventional AC-coupled RES-ESS facility includes an aggregate RESinverter output capacity that is matched to a POGI limit. A slightdegree (e.g., 2%-3%) of excess RES inverter capacity may theoreticallybe provided in a conventional RES-ESS in order to accommodate reactivepower demand and losses, but any higher levels of excess RES invertercapacity have not been adopted to avoid violating FERC interconnectionprocedures and the LGIA as described previously herein in theBackground.

In certain embodiments, a RES-ESS facility comprises a RES that producesRES DC electric power; an ESS configured to be charged with electricpower produced by the RES; at least one first power inverter coupledbetween the RES and a grid interconnection point, and at least onesecond power inverter coupled (i) between the ESS and the gridinterconnection point, and (ii) between the at least one first powerinverter and the grid interconnection point. The at least one firstpower inverter is configured to convert RES DC electric power to RES ACelectric power. The at least one second power inverter is configured to(a) convert RES AC electric power to ESS DC electric power when chargingthe ESS with RES AC electric power, and (b) convert ESS DC electricpower to ESS AC electric power when discharging the ESS AC electricpower to the electric grid. An aggregate output capacity of the at leastone first power inverter is sized to exceed the POGI limit; and theRES-ESS facility is configured to divert RES AC electric power to the atleast one second power inverter in an amount sufficient to avoidsupplying RES AC electric power to the electric grid in excess of thePOGI limit.

In certain embodiments of an AC oversized RES-ESS facility, theaggregate output capacity of the at least one first power inverter issized to exceed the POGI limit by at least 10%, by at least 30%, by atleast 50%, by at least 70%, by at least 100%, or another thresholdspecified herein. In certain embodiments, the foregoing minimumthresholds may optionally be capped (where appropriate) by values of (A)120%, (B) 150%, (C) 200%, or the sum of (i) the POGI limit and (ii) acapacity of the ESS. In certain embodiments, the aggregate outputcapacity of the at least one first power inverter is sized to equal asum of (i) the POGI limit and (ii) a capacity of the ESS. In certainembodiments, the at least one first power inverter may comprise multiplepower inverters.

Technical benefits of an AC overbuilt RES-ESS facility include theability to provide a higher capacity factor (e.g., 50-60% for an ACoverbuilt PV-BESS facility, as compared to a range of perhaps 30-40% fora conventional PV-BESS facility). Such a facility is capable ofdelivering more renewable energy with existing transmission resources(which is expensive and time-consuming to build). A lower cost of energymay be attained because fixed development project costs may be amortizedover more annual megawatt-hours of production.

As noted above, an AC overbuilt RES-ESS facility is also suitable forproviding a high level of fixed firm capacity (e.g., at least 70%, atleast 80%, at least 90%, at least 95%, or at least 99% of a POGI limit)for a long duration (e.g., at least 6 hours per day, at least 8 hoursper day, at least 12 hours per day, at least 16 hours per day, at least20 hours per day, or 24 hours per day in certain embodiments). Incertain embodiments, long-term weather data may be utilized when sizingan ESS and the at least one first inverter to permit the foregoingcapacity and duration thresholds to be achieved with a confidence windowof at least 90%, at least 95%, at least 98%, or at least 99% over allforeseeable weather conditions. In certain embodiments, the confidencewindow corresponds to a number of days per month or per year in whichthe specified fixed firm capacity and long duration is attained. Theability to provide a high level of fixed firm capacity enables an ACoverbuilt RES-ESS facility to replace conventional baseload assets(e.g., gas-fired, coal-fired, or nuclear power plants) and improve gridstability.

In certain embodiments, a method for controlling a RES-ESS facilityconfigured to supply electric power to an electric grid at a gridinterconnection point is provided, with the RES-ESS facility including arenewable energy source (RES) and an energy storage system (ESS)chargeable with electric power produced by the RES, and the RES-ESSfacility having a point of grid interconnect (POGI) limit. The methodcomprises: providing at least one first power inverter coupled betweenthe RES and the grid interconnection point, wherein the at least onefirst power inverter is configured to convert RES DC electric power toRES alternating current (AC) electric power, and an aggregate outputcapacity of the at least one first power inverter is sized to exceed thePOGI limit; providing at least one second power inverter coupled (i)between the ESS and the grid interconnection point, and (ii) between theat least one first power inverter and the grid interconnection point,wherein the at least one second power inverter is configured to (a)convert RES AC electric power to ESS DC electric power when charging theESS with RES AC electric power, and (b) convert ESS DC electric power toESS AC electric power when discharging the ESS AC electric power to theelectric grid; and while supplying a first portion of the RES ACelectric power to the electric grid, diverting a second portion of theRES AC electric power to the at least one second power inverter in anamount sufficient to avoid supplying RES AC electric power to theelectric grid in excess of the POGI limit.

In certain embodiments, the method further comprises supplying RES ACelectric power to the electric grid at a fixed firm capacity of at least80% (or at least 90%, or at least 95%, or 100%) of the POGI limit for aduration of at least 8 hours per day, or at least 12 hours per day, orat least 16 hours per day, or another threshold specified therein. Incertain embodiments, the supplying of RES AC electric power to theelectric grid for the specified fixed firm capacity and duration isperformed for at least 90%, at least 95%, or at least 99% of the days ina specified month or year.

FIGS. 6A-6C provide basis for comparing component sizing and attributesof an AC overbuilt RES-ESS facility (according to FIG. 6B) relative to aconventional AC-coupled RES-ESS facility (according to FIG. 6A) andrelative to a DC coupled RES-ESS facility (according to FIG. 6C). Valuesfor RES capacity, inverter capacity, and point of interconnect limitsprovided in FIGS. 6A-6C are provided to promote ease of understanding,without intending to limit a scope of protection.

FIG. 6A is a diagram showing relative sizes of a RES 92 (e.g.,comprising direct current photovoltaic modules), power inverters 94, anda point of interconnect limit (previously referred to herein as POGIlimit) for a conventional RES facility 90 coupled with an AC electricgrid at a grid interconnection point 96. As shown in FIG. 6A, the RES 92may be configured to output 135 MW, the power inverters 94 (which serveto convert RES DC electric power to AC electric power) may have anoutput capacity of no greater than 103 MW, and the POGI limit may be 100MW. A ratio of RES DC power supplied from the RES 92 to the powerinverters 94 may be about 1.3, while a ratio of RES DC power to the POGIlimit may be 1.35. A mismatch between RES DC power and a capacity of thepower inverters 94 results in a first portion of clipped or lost energy93, and a mismatch between the capacity of the power inverters 94 andthe POGI limit results in a second portion of clipped or lost energy,that is wasted when the RES 92 is generating RES DC power at fullcapacity.

FIG. 6B is a diagram showing relative sizes of a RES 102 (e.g.,comprising direct current photovoltaic modules), power inverters 104,and a point of interconnect limit (previously referred to herein as POGIlimit) for an AC overbuilt RES-ESS facility 100 coupled with an ACelectric grid at a grid interconnection point 106, according to oneembodiment of the present disclosure. As shown in FIG. 6B, the RES 102may be configured to output 175 MW, the power inverters 104 (which serveto convert RES DC electric power to RES AC electric power) may have anoutput capacity of 135 MW, and the POGI limit may be 100 MW. AnAC-coupled ESS 108 (having an associated power inverter (not shown)) isprovided to receive and store any portion of the RES AC electric outputthat exceeds the POGI limit, thereby avoiding feeding excess energy tothe electric grid, while avoiding a potential energy loss 105 if the ESS108 were not present. A ratio of RES DC power supplied from the RES 102to the power inverters 104 may be about 1.3, while a ratio of RES DCpower to the POGI limit may be 1.75. A mismatch between RES DC power anda capacity of the power inverters 104 results in clipped or lost energy103 that is wasted when the RES 92 is generating RES DC power at fullcapacity. In certain embodiments, the capacity of the power inverters104 may be increased relative to the value stated in FIG. 6B to one ofthe thresholds stated herein (e.g., to be equal to a sum of the POGIlimit and the capacity of the ESS 108). If it is desired to reduce orlimit the clipped or lost energy 103, the power inverters 104 may besized to have a capacity closer or equal to an output capacity of theRES 102.

Although FIG. 6B depicts a modest degree of oversizing of an ESS andpower inverters, it is to be appreciated that any suitable degree ofoversizing may be provided to enable a RES-ESS to provide a desiredfixed firm capacity level and desired duration with a desired degree ofconfidence.

FIG. 6C is a diagram showing relative sizes of a RES 112, powerinverters 114, and a point of grid interconnect limit for a DC-coupledRES-ESS facility 110 coupled with an AC electric grid at a gridinterconnection point 116, wherein a DC-coupled ESS 118 is arranged toreceive and store RES DC electric output that exceeds the capacity ofthe power inverters 114 (thereby avoiding a potential energy loss 113 ifthe ESS 118 were not present). A ratio of RES DC power supplied from theRES 112 to the power inverters 114 may be about 1.7, while a ratio ofRES DC power to the POGI limit may be 1.75. A mismatch between an outputcapacity of the power inverters 114 and the POGI limit results inclipped or lost energy 115 that may be wasted when the RES 112 isgenerating RES DC power at full capacity and the power inverters 114 areoperating at capacity.

Differences in operation and performance between a non-overbuilt RES-ESSfacility and an AC overbuilt RES-ESS facility may be understood uponcomparison of FIGS. 7A and 7B.

FIG. 7A is a modeled output plot for a non-overbuilt AC-coupled RES-ESSfacility having power inverter capacity that is matched to a point ofgrid interconnect limit. FIG. 7A provides superimposed plots of RESproduction (i.e., photovoltaic or “PV”), combined RES-ESS output (i.e.,PV plus storage or “PV+S”), and point of interconnect (POI) limit (whichis also referred to herein as POGI limit”). As shown, the POI limit is100 MW, the peak PV output (i.e., as direct current, before beingclipped by the inverter capacity limit close to the POGI power limit) isabout 10% higher than the POI limit, and the PV+S output equals the POIlimit for only about one hour during the day.

FIG. 7B is a modeled output plot for an AC overbuilt RES-ESS facilityhaving a power inverter capacity that significantly exceeds a point ofgrid interconnect limit according to one embodiment of the presentdisclosure. FIG. 7B provides superimposed plots of RES production (i.e.,photovoltaic or “PV”), combined RES-ESS output (i.e., PV plus storage or“PV+S”), and point of interconnect (POI) limit (which is also referredto herein as POGI limit”). As shown, the POI limit is 100 MW, the peakPV output (as alternating current, after inversion) is about 50% higherthan the POI limit, and the PV+S output equals the POI limit for abouteight hours or longer during the day. The area between the plotted POIlimit and the PV production represents energy available to be stored inan energy storage device (e.g., battery array). Presence of ahigh-capacity energy storage device with oversized inverter capacity(exceeding the POI limit) permits excess energy produced by the PV array(i.e., power in excess of the POI limit) to be stored. This permits thePV+S output to function similarly to a baseload unit between about 09:00and 17:00 by providing a fixed firm capacity during this period, whilestill permitting excess energy to be stored for discharge later in theday after PV production has ramped down.

FIG. 8 is a modeled output plot for an AC overbuilt RES-ESS facilityhaving power inverter capacity that exceeds a point of grid interconnectlimit according to one embodiment of the present disclosure, withsuperimposed plots of RES production (photovoltaic megawatts, or “PVMW”), combined RES-ESS output (“net plant MW), and state of charge (“SOC%”) of the ESS. In the modeled configuration, the ESS has a capacity tocharge or discharge 300 MW, the ESS has a maximum output capacity ofgreater than 500 MW (as alternating current, after inversion), and thePOGI limit is 400 MW. As shown, the combined RES-ESS AC output suppliedto the grid is 400 MW from about 08:30 to about 17:30, with such amountbeing equal to the POGI limit for the facility. During the sameinterval, RES production exceeds the POGI limit, with the energy of thisovergeneration being used to charge the ESS (as shown by the risingstate of charge). When RES production starts to fall around 17:30,control of the ESS is switched from a charging mode to a dischargingmode, and output of the ESS is converted to AC to supply power to thegrid. ESS AC output of 300 MW is supplied to the grid from about 18:00to about 22:30 and then drops to zero by 23:00, thereby readying the ESSto be charged the next day to receive generation of the RES that exceedsthe POGI limit for the facility. As shown, the facility may be used tosupply power to the grid at a fixed value equal to the POGI limit formore than 9 hours, and to further supply power to the grid at a valueequal to 75% of the POGI limit for more than 4 additional hours. Theability of the AC overbuilt RES-ESS facility to supply fixed firmcapacity at or near the POGI limit for long sustained periods at a highcapacity represents a significant departure from conventional RES-ESSfacilities.

Additional differences in operation and performance between anon-overbuilt RES-ESS facility and an AC overbuilt RES-ESS facility maybe understood upon comparison of FIGS. 9A and 9B.

FIG. 9A is a modeled output plot for an AC-coupled RES-ESS facilityhaving power inverter capacity matched to a point of grid interconnectlimit. FIG. 9A provides superimposed plots of RES production (i.e.,photovoltaic or “PV”), combined RES-ESS output (i.e., PV plus storage or“PV+S” output), ESS power output (i.e., “BESS power”), and ESS state ofcharge (i.e., “BESS SOC”). As shown, maximum PV production of 100 MW isachieved from about 08:00 to about 16:30, with a portion of thisproduction being used to charge the ESS (as evidenced by the rising SOCvalue and the negative ESS power output) during this period. When RESproduction starts to fall and maximum SOC is attained around 16:00,control of the ESS is switched from a charging mode to a dischargingmode, and output of the ESS is converted to AC to supply power to thegrid. Combined RES-ESS output of 100 MW equal to the POGI limit isachieved for about 4.5 hours, from 16:00 to about 20:30, and then dropsto zero by 21:00, thereby readying the ESS to be charged the next day.

FIG. 9B is a modeled output plot for an AC overbuilt RES-ESS facilityhaving power inverter capacity that significantly exceeds a point ofgrid interconnect limit according to one embodiment of the presentdisclosure. FIG. 9B provides superimposed plots of RES production (i.e.,photovoltaic or “PV”), combined RES-ESS output (i.e., PV plus storage or“PV+S” output), ESS power output (i.e., “BESS power”), and ESS state ofcharge (i.e., “BESS SOC”) for a facility having a POGI limit of 100 MW.As shown, maximum PV production of about 150 MW is achieved from about08:00 to about 16:30, with a portion of this production being used tocharge the ESS (as evidenced by the rising SOC value and the negativeESS power output) during this period. When RES production starts to falland maximum SOC is attained around 16:00, control of the ESS is switchedfrom a charging mode to a discharging mode, and output of the ESS isconverted to AC to supply power to the grid. Combined RES-ESS output of100 MW equal to the POGI limit is achieved for more than about 13 hours,from before 08:00 to about 21:00, and then drops to zero by 22:00,thereby readying the ESS to be charged the next day. Presence of ahigh-capacity ESS and oversized inverter capacity (exceeding the POGIlimit) permits excess energy produced by the ESS array (i.e., power inexcess of the POI limit) to be stored, and permits the PV+S output tofunction similarly to a baseload unit between about 08:00 to about 21:00by providing a fixed firm capacity during this period.

B. RES-ESS Control Method Mode Using SOC target-based POGI Cap

One aspect of the present disclosure is directed to a method forcontrolling a RES-ESS facility that uses a time-dependent forecast ofelectrical energy production by the RES and a state of charge (SOC)schedule for the ESS to calculate a SOC target-based POGI cap that isless than the (predetermined fixed) POGI limit, with the SOCtarget-based POGI cap representing a peak power output value for theRES-ESS facility that is as low as possible while still ensuring thatthe SOC schedule is satisfied. The method further comprises using theSOC target-based POGI cap in conjunction with the time-dependentforecast of electrical energy production by the RES and the state ofcharge (SOC) schedule for the ESS to generate a time-varyingcharge/discharge control signal for the ESS, with the control signalbeing configured to ensure satisfaction of the SOC schedule.

The SOC target-based POGI cap represents a suggested peak power limitthreshold that maximizes headroom (e.g., spinning reserve capacity) of aRES-ESS facility, thereby enhancing the ability of the RES-ESS facilityto provide ancillary services (and to charge a grid operator forproviding ancillary services). In practice, the grid operator may chooseto set (and utilize) the SOC target-based POGI cap.

In certain embodiments, a method comprises: utilizing (A) atime-dependent forecast of electrical energy production by the RES and(B) a state of charge (SOC) schedule to calculate a SOC target-basedPOGI cap that is less than the POGI limit, wherein the SOC target-basedPOGI cap represents a peak power output value for the RES-ESS that is aslow as possible while still ensuring that the SOC schedule is satisfied;and utilizing (A) the time-dependent forecast of electrical energyproduction by the renewable electrical energy generation resource, (B)the state of charge (SOC) schedule for the electrical energy storagedevice including at least one SOC target value, and (C) the SOCtarget-based POGI cap, to generate a time-varying charge/dischargecontrol signal for the ESS, wherein the time-varying charge/dischargecontrol signal is configured to ensure that the SOC schedule issatisfied.

In certain embodiments, a SOC target-based POGI cap may be estimatedusing an optimization algorithm to solve for an optimal upper thresholdsuch that the amount of energy charged is equal to the required energyto reach a maximum value of the SOC in a specified period, wherein themaximum value may be termed the Maximum State of Energy. In particular,the method may involve solving for x (representing the SOC target-basedPOGI cap) such that:

${{\sum\limits_{i = 1}^{n}{\left( {{PV}\mspace{14mu}{Forecast}\mspace{14mu}{{Power}\left\lbrack {{Power} > x} \right\rbrack}} \right)({Wh})}} - {x \times {n({Wh})}}}=={{Max}\mspace{14mu}{State}\mspace{14mu}{of}\mspace{14mu}{Energy}\mspace{14mu}({Wh})}$

wherein:

-   -   ‘n’ is the number of forecasted power values in a target        interval;    -   ‘x’ is the SOC target-based POGI cap (threshold); and    -   Max State of Energy is a function of the configurable Max SOC        parameter.

In certain embodiments, the SOC target-based POGI cap may be generatedusing a computer-implemented, iterative root-finding algorithm. Onenon-limiting example is the Newton-Raphson method. In certainembodiments, the SOC target-based POGI cap may be generated using acomputer-implemented, matrix-based root-finding algorithm.

Results of utilizing a SOC target-based POGI cap are shown in FIG. 10,which is a modeled output plot for an AC overbuilt RES-ESS facilityhaving power inverter capacity that exceeds a point of grid interconnectlimit according to one embodiment of the present disclosure, withsuperimposed plots of RES production, combined RES-ESS output, state ofcharge of the ESS, and ESS power output. FIG. 10 shows a result ofcalculating a SOC target-based POGI cap (also termed Peak Power Limitthreshold in FIG. 10) that provides a SOC of 95% of capacity before theend of a day.

In certain embodiments, a method involving a SOC target-based POGI capfurther comprises periodically updating the generation of thetime-varying charge/discharge control signal based upon at least one ofthe following items (i) or (ii): (i) an updated time-dependent forecastof electrical energy production; or (ii) an updated SOC schedule.

In certain embodiments, the method further comprises periodicallyupdating the generation of the time-varying control signal uponexpiration of a refresh period, wherein the periodic updating comprisescomputing and using a new basepoint value for aggregated energy suppliedfrom the renewable electrical energy generation resource and theelectrical energy storage device to an electrical grid upon expirationof the refresh period. In certain embodiments, the refresh period isconfigurable, and the time-varying charge/discharge control signal ispermitted to change no more than once per refresh period. In certainembodiments, the time-varying charge/discharge control signal ispermitted to change only once within a configurable refresh period, tokeep aggregated power output of a RES-ESS facility constant during therefresh period, thereby enabling participation in energy markets and/orenergy balance markets. In certain embodiments, the refresh period isconfigurable by an operator of the RES-ESS facility.

In certain embodiments, the electrical energy storage device is chargedexclusively from the renewable electrical energy generation resource.

In certain embodiments, the method further comprises altering thetime-varying charge/discharge control signal responsive to a differencebetween forecasted production and actual production of at least oneelectric generation facility to ensure that the SOC schedule issatisfied.

In certain embodiments, the time-dependent forecast of electrical energyproduction comprises an ensemble based on of two or more of thefollowing: on-site sky imaging, satellite imaging, and meteorologicalmodeling.

In certain embodiments, wherein the time-dependent forecast ofelectrical energy production comprises a refresh rate that determineshow often a new basepoint value for aggregated photovoltaic plus storageenergy supplied to an electric grid (PV+S output basepoint value) iscomputed. In certain embodiments, a pre-existing PV+S Output value isused until a new PV+S output basepoint value is computed.

In certain embodiments, the renewable electrical energy generationresource comprises a photovoltaic array, the electrical energy storagedevice comprises a battery array, and the time-dependent forecast ofelectrical energy production comprises a solar production forecast.

In certain embodiments, the renewable electrical energy generationresource comprises at least one wind turbine, the electrical energystorage device comprises a battery array, and the time-dependentforecast of electrical energy production comprises a wind productionforecast.

FIG. 11 is schematic diagram of a generalized representation of acomputer system 200 that can be included as one or more components of asystem for controlling a renewable electrical energy generation resourceand an electrical energy storage device chargeable with electric powerproduced by the renewable electrical energy generation resource,according to one embodiment. The computer system 200 may be adapted toexecute instructions from a computer-readable medium to perform theseand/or any of the functions or processing described herein.

The computer system 200 may include a set of instructions that may beexecuted to program and configure programmable digital signal processingcircuits for supporting scaling of supported communications services.The computer system 200 may be connected (e.g., networked) to othermachines in a local area network (LAN), an intranet, an extranet, or theInternet. While only a single device is illustrated, the term “device”shall also be taken to include any collection of devices thatindividually or jointly execute a set (or multiple sets) of instructionsto perform any one or more of the methodologies discussed herein. Thecomputer system 200 may be a circuit or circuits included in anelectronic board or card, such as a printed circuit board (PCB), aserver, a personal computer, a desktop computer, a laptop computer, apersonal digital assistant (PDA), a computing pad, a mobile device, orany other device, and may represent, for example, a server or a user'scomputer.

The computer system 200 in this embodiment includes a processing deviceor processor 202, a main memory 204 (e.g., read-only memory (ROM), flashmemory, dynamic random access memory (DRAM), such as synchronous DRAM(SDRAM), etc.), and a static memory 206 (e.g., flash memory, staticrandom access memory (SRAM), etc.), which may communicate with eachother via a data bus 208. Alternatively, the processing device 202 maybe connected to the main memory 204 and/or static memory 206 directly orvia some other connectivity means. The processing device 202 may be acontroller, and the main memory 204 or static memory 206 may be any typeof memory.

The processing device 202 represents one or more general-purposeprocessing devices, such as a microprocessor, central processing unit(CPU), or the like. In certain embodiments, the processing device 202may be a complex instruction set computing (CISC) microprocessor, areduced instruction set computing (RISC) microprocessor, a very longinstruction word (VLIW) microprocessor, a processor implementing otherinstruction sets, or other processors implementing a combination ofinstruction sets. The processing device 202 is configured to executeprocessing logic in instructions for performing the operations and stepsdiscussed herein.

The computer system 200 may further include a network interface device210. The computer system 200 may additionally include at least one input212, configured to receive input and selections to be communicated tothe computer system 200 when executing instructions. The computer system200 also may include an output 214, including but not limited to adisplay, a video display unit (e.g., a liquid crystal display (LCD) or acathode ray tube (CRT)), an alphanumeric input device (e.g., akeyboard), and/or a cursor control device (e.g., a mouse).

The computer system 200 may or may not include a data storage devicethat includes instructions 216 stored in a computer readable medium 218.The instructions 216 may also reside, completely or at least partially,within the main memory 204 and/or within the processing device 202during execution thereof by the computer system 200, the main memory 204and the processing device 202 also constituting computer readablemedium. The instructions 216 may further be transmitted or received overa network 220 via the network interface device 210.

While the computer readable medium 218 is shown in an embodiment to be asingle medium, the term “computer-readable medium” should be taken toinclude a single medium or multiple media (e.g., a centralized ordistributed database, and/or associated caches and servers) that storethe one or more sets of instructions. The term “computer readablemedium” shall also be taken to include any medium that is capable ofstoring, encoding, or carrying a set of instructions for execution bythe processing device and that cause the processing device to performany one or more of the methodologies of the embodiments disclosedherein. The term “computer readable medium” shall accordingly be takento include, but not be limited to, solid-state memories, an opticalmedium, and/or a magnetic medium.

In certain embodiments, systems and apparatuses disclosed herein mayutilize a non-transitory computer readable medium containing programinstructions for controlling, by at least one processor, (i) a renewableelectrical energy generation resource and (ii) an electrical energystorage device chargeable with electric power produced by the renewableelectrical energy generation resource, the method comprising utilizing,by the at least one processor, (A) a time-dependent forecast ofelectrical energy production by the RES and (B) a state of charge (SOC)schedule to calculate a SOC target-based POGI cap that is less than thePOGI limit, wherein the SOC target-based POGI cap represents a peakpower output value for the RES-ESS that is as low as possible whilestill ensuring that the SOC schedule is satisfied. The method furthercomprises utilizing, by the at least one processor, (A) thetime-dependent forecast of electrical energy production by the renewableelectrical energy generation resource, (B) the state of charge (SOC)schedule for the electrical energy storage device including at least oneSOC target value, and (C) the SOC target-based POGI cap, to generate atime-varying charge/discharge control signal for the ESS, wherein thetime-varying charge/discharge control signal is configured to ensurethat the SOC schedule is satisfied.

In certain embodiments, the program instructions contained in thecomputer readable medium may be configured to perform additional methodsteps as disclosed herein.

C. Method for Implementing Power Delivery Transaction for PotentialRES-ESS Output

As noted previously herein, if renewable energy producers are rewardedfor energy generation alone, these producers may be discouraged fromproviding ancillary services. Additionally, the capital expenses fordeveloping the projects are typically amortized over the expectedgeneration, and investors of these projects need certainty in theexpected generation in order to contribute capital for project funding.To address these issues, one aspect of the present disclosure isdirected to a method for implementing a power delivery transactionbetween a buyer and seller for potential electrical energy output of aRES-ESS facility. Such a method includes periodically estimating totalpotential electrical energy output of the RES during at least oneretrospective time windows utilizing a signal indicative of one or moresensed parameters. The method further includes comparing the totalpotential electrical energy output of the RES to a POGI limit for thefacility to identify potential RES overgeneration during the timewindow(s), and identifying an amount of charged potential RESovergeneration that was charged to the ESS during the time window(s).The method further includes charging the buyer for undeliveredelectrical energy if charged potential RES overgeneration is less thanpotential RES overgeneration during the time window(s). Such a method isspecifically intended to give RES-ESS investors certainty in expectedrevenues by metering potential generation above a POGI limit.

The method provides a financial incentive for a utility (or other gridoperator) to discharge an ESS each day so that the ESS is empty by thenext morning and ready to accept a full charge again. The method permitsestimation of an amount of energy that could have been stored in an ESS,but was not stored if the utility or grid operator did not fullydischarge the ESS. Such a method further provides a basis for theRES-ESS facility owner to be paid for the estimated amount of energythat did not get stored as a result of the utility or grid operator notfully discharge the ESS prior to the start of a new day. Implementationof such a method provides an incentive for investors to supportconstruction of AC-overbuilt RES-ESS facilities without hamperingflexibility of grid operators to control generation resources, byensuring certainty of a revenue stream to the RES-ESS facility even ifthe utility elects not to fully discharge an ESS.

In certain embodiments, a method for implementing a power deliverytransaction between a buyer and seller for potential electrical energyoutput of an integrated renewable energy source and energy storagesystem (RES-ESS) facility comprises: periodically estimating totalpotential electrical energy output of the RES during at least oneretrospective time window utilizing a signal indicative of one or moresensed parameters; comparing the estimated total potential electricalenergy output of the RES to a point of grid interconnect (POGI) limitfor the RES-ESS facility to identify potential RES overgeneration duringthe at least one retrospective time window, wherein potential RESovergeneration equals potential RES electrical energy output in excessof the POGI limit during the at least one retrospective time window;identifying an amount of charged potential RES overgeneration,calculated as potential RES overgeneration charged to the ESS during theat least one retrospective time window; and charging the buyer forundelivered electrical energy if charged potential RES overgeneration isless than potential RES overgeneration during one or more time windowsof the at least one retrospective time window.

In certain embodiments, the method further comprises identifying anamount of uncharged potential RES overgeneration, calculated aspotential RES overgeneration not charged to the ESS during the at leastone retrospective time window; wherein an amount charged to the forundelivered electrical energy is based on a deemed delivered RESovergeneration value that is identified according to the followinglogical sequence: (i) if potential RES overgeneration equals zero, thenthe deemed delivered RES overgeneration value equals zero, else (ii) ifcharged potential RES overgeneration is greater than or equal topotential RES overgeneration, then the deemed delivered RESovergeneration value equals zero, else (iii) if charged RESovergeneration is less than potential RES overgeneration, then thedeemed delivered RES overgeneration value equals the lesser of thefollowing items (a) and (b): (a) uncharged potential RES overgeneration,and (b) potential RES overgeneration minus charged RES overgeneration.

In certain embodiments, the at least one retrospective time windowcomprises a plurality of time periods. In certain embodiments each timeperiod of the plurality of time periods is less than one hour (e.g.,each time period may be five minutes, one minute, or another suitableinterval).

In certain embodiments, the one or more time windows comprises asummation of multiple time windows of the at least one retrospectivetime window. In certain embodiments, the summation of multiple timewindows corresponds to a period of one day.

In certain embodiments, the RES comprises a photovoltaic array, and theone or more sensed parameters comprise irradiance sensed at one or morelocations at the RES-ESS facility.

In certain embodiments, the RES comprises one or more wind turbines, andthe one or more sensed parameters comprise wind speed sensed at one ormore locations at or above the RES-ESS facility.

In certain embodiments, the RES-ESS facility is configured to supplyenergy to an electrical grid at a voltage of at least 33 kV or at least66 kV. In certain embodiments, the ESS is configured to be changedexclusively from the RES.

In certain embodiments, a RES may be oversized relative to acorresponding ESS of a RES-ESS facility, to ensure that the RES canfully charge the ESS (e.g., for a RES embodying a PV array in winter orin a season when more clouds are expected). The potential excessproduction from the RES might exceed the full energy capacity of theESS. In such an instance, a maximum limit may be set on the calculatedpotential excess energy production from the RES per day, set by thecapacity of the ESS, so that the buyer would not be charged forpotential overgeneration in excess of could be absorbed by the ESS canabsorb. This maximum limit would still allow charging for potentialenergy the RES could have produced, but that was not stored in the ESSbecause the buyer had not discharged the ESS from the previous day Insuch an instance, the method may further comprise capping an amount ofcharged potential RES overgeneration based on a capacity of the ESS, ifthe potential RES overgeneration exceeds a capacity of the ESS.

While specific aspects, features and illustrative embodiments have beendisclosed herein, it will be appreciated that the disclosure extends toand encompasses numerous other variations, modifications, andalternative embodiments, as will suggest themselves to those of ordinaryskill in the pertinent art, based on the disclosure herein. Variouscombinations and sub-combinations of the structures described herein arecontemplated and will be apparent to a skilled person having knowledgeof this disclosure. Any of the various features and elements asdisclosed herein may be combined with one or more other disclosedfeatures and elements unless indicated to the contrary herein.Correspondingly, the invention as hereinafter claimed is intended to bebroadly construed and interpreted, as including all such variations,modifications, and alternative embodiments, within its scope andincluding equivalents of the claims.

1.-22. (canceled)
 23. A method for controlling a system comprising anintegrated renewable energy source (RES) and energy storage system(ESS), the method comprising: determining a peak power threshold tolimit a peak power output of the system to an electric grid, wherein thepeak power threshold is determined based at least in part on (a) atime-dependent forecast of electrical energy production by the RES and(b) a state of charge (SOC) schedule of the ESS; and generating atime-varying control signal based at least in part on the peak powerthreshold, wherein the time-varying control signal is used to controlcharging and discharging of the ESS thereby ensuring the SOC schedule ofthe ESS is satisfied.
 24. The method of claim 23, wherein the peak powerthreshold is estimated using an optimization algorithm.
 25. The methodof claim 24, wherein the optimization algorithm comprises an iterativeroot-finding algorithm or matrix-based root-finding algorithm.
 26. Themethod of claim 23, wherein the peak power threshold is less than amaximum electric power value to be supplied to the electric grid. 27.The method of claim 23, further comprising periodically updating thegeneration of the time-varying control signal based upon at least one ofthe following: (i) an updated time-dependent forecast of electricalenergy production; or (ii) an updated SOC schedule.
 28. The method ofclaim 23, further comprising periodically updating the generation of thetime-varying control signal upon expiration of a refresh period basedupon at least a value for aggregated energy supplied from the RES andthe ESS to the electric grid upon the expiration of the refresh period.29. The method of claim 28, wherein the refresh period is configurableby an operator of the system.
 30. The method of claim 28, wherein thetime-varying control signal changes no more than once in the refreshperiod.
 31. The method of claim 28 wherein the value for aggregatedenergy supplied from the RES and the ESS is updated upon expiration of anew refresh period.
 32. The method of claim 23, wherein the ESS ischarged exclusively from the RES.
 33. The method of claim 23, furthercomprising altering the time-varying control signal responsive to adifference between forecasted production and actual production of thesystem to ensure that the SOC schedule is satisfied.
 34. The method ofclaim 23, wherein the time-dependent forecast of electrical energyproduction is based on one or more of the following: on-site skyimaging, satellite imaging, or meteorological modeling.
 35. The methodof claim 23, wherein the RES comprises a photovoltaic array, the ESScomprises a battery array, and the time-dependent forecast of electricalenergy production comprises a solar production forecast.
 36. The methodof claim 23, wherein the RES comprises at least one wind turbine, theESS comprises a battery array, and the time-dependent forecast ofelectrical energy production comprises a wind production forecast. 37.The method of claim 23, further comprising maintaining frequency,voltage, and power load of the system.